L9857-TR-LF

PMIC – Gate Drivers refer to the application of integrated circuits (or ICs) specifically designed to drive the gate of power transistors. The L9857-TR-LF is one such PMIC gate driver, which is extensively used in various industries for power automation and/or regulation purposes.

The L9857TR-LF is a 3-channel integrated circuit for insulated gate bipolar transistors (IGBTs). It contains a system that facilitates two low side MOSFETs, two high side IGBTs, and one high side PWM output. The maximum driver current on each of the outputs is 8A while its PWM output can have a maximum of 10A of peak current.

The other features of L9857TR-LF includes input/output compatibility of 5.5V to 60V, temperature range of -40°C to 150°C, PWM frequency of 10kHz, and 8MHz oscillator frequency with less than ±2% accuracy. The L9857TR-LF is available in a 29 pin SOT143D package and can be used with standard logic level as well as dual-complementary inputs.

The L9857TR-LF is primarily used for switching high amperage loads, such as motors, pumps, and various industrial equipment. The integrated circuit has built-in protection from over-voltage, over-current, and under-voltage. The built-in thermistor and current sensing also extend the life expectancy of the device. This makes it suitable for use in industrial and medical equipment, LED lighting, power utilities, automotive/locomotive power inverter and uninterruptable power supplies.

The working principle of this gate driver is quite simple. It acts as a synchronous STM (switched-mode) gate and works on a pulse width modulation (PWM) technology. Essentially, the PWM frequency is inversely proportional to the motor speed. This means the gate driver can generate frequency changes that can be seen as a variation in voltage levels and as a result, can be used to control motor speed.

The PWM output of the gate driver creates a time varying square wave with phase shift of either 90° or 180° depending on the pulse width. This phase shift turns the motor on or off depending on the duty cycle of the PWM output.

In conclusion, the L9857TR-LF is a simple and cost-efficient integrated circuit gate driver particularly designed for driving motors and other high amperage loads. With its wide input/output compatibility and varying PWM frequency, this gate driver makes it a fundamental component for power automation and regulation purposes.